Journal of the Czech Geological Society 51/34(2006)

259

Mineralogy of dumortierite-bearing abyssal pegmatites
at Starkoè and Bìstvina, Kutná Hora Crystalline Complex
Mineralogie abysálních pegmatitù s dumortieritem
ze Starkoèe a Bìstviny, Kutnohorské krystalinikum(8 figs, 3 tabs)
JAN CEMPÍREK1, 2  MILAN NOVÁK2
1
2

Department of Mineralogy and Petrography, Moravian Museum, Zelný trh 6, CZ-659 37 Brno
Institute of Geological Sciences, Masaryk University, Kotláøská 2, CZ-611 37 Brno

Abyssal pegmatites from Starkoè and Bìstvina are typical examples of the AB-BBe subclass pegmatites in the Bohemian Massif. The
features typical for origin and evolution of both abyssal pegmatites are better preserved in the pegmatite at Starkoè, where, based onparagenetic relationships, three distinct assemblages were recognized: (i) Primary igneous assemblage: plagioclase I + quartz I + muscovite+ garnet III + tourmaline I + dumortierite I + chrysoberyl; (ii) Prograde metamorphic assemblage: quartz II + plagioclase II + kyanite +K-feldspar + staurolite + tourmaline II + dumortierite II; (iii) Retrograde metamorphic assemblage: pyrophyllite and kaolinite. Plagioclase,quartz and muscovite are major minerals in the pegmatite veinlet; the most common accessory minerals include tourmaline, dumortierite,
garnet, K-feldspar and kyanite, whereas only trace amounts of chrysoberyl, staurolite and several very rare accessory minerals were found.
Composition of tourmaline is controlled by the two-stage evolution of the pegmatite. Primary tourmaline I from Starkoè exhibits crystallization trend expressed by the substitution (Y,ZAl TAl)(Y,ZR2+ TSi4+)-1. Prograde metamorphic event introduced additional Fe and Mg from thehost rock into the system and remobilization of B allowed crystallization of Mg-enriched, rather homogeneous tourmaline II. Strakoè and allother known pegmatites of AB-BBe subclass in the Bohemian Massif occur in the Gföhl Unit, along the easternmost border of the
Moldanubicum. Pegmatite host rocks exhibit HP metamorphic conditions and low degree of MP overprint. Such metamorphic evolution isa typical feature of host rocks of similar abyssal pegmatites in high-grade terrains in Antarctica, Norway and Madagascar.
Key words: abyssal pegmatite; dumortierite; tourmaline; Kutná Hora Crystalline Complex

1. Introduction
Abyssal (metamorphic) pegmatites are related to anatectic processes in high-grade metamorphic rocks of upper
amphibolite to granulite facies. Their mineral assemblages are mostly simple, including common rock-forming
minerals such as muscovite, biotite, garnet, tourmaline,
cordierite and Al2SiO5 modifications besides major minerals  quartz, plagioclase and/or K-feldspar. Abyssal
pegmatites form dikes, lenses or irregular bodies commonly about several cm to several dm thick, hosted largely in metapelitic rocks. Their internal structure is commonly simple, complexly zoned pegmatites are rare.
Based on the accessory minerals, the abyssal pegmatites
were subdivided on four subclasses  AB-HREE, ABLREE, AB-U and AB-BBe (Èerný  Ercit 2005).
Abyssal pegmatites of the AB-BBe subclass were described from several localities in high-grade metamorphic
terranes e.g., in Antarctica (Grew 1981, 1998, Grew etal. 1998a, b, 2000), Madagascar (Grew et al. 1998b), Sri
Lanka (Grew et al. 1995), India (Soman 1986), Norway(Huijismans et al. 1982), Zambia (áèek  Vrána 2002)
and Austria (Ertl et al. 1997, Kalt et al. 2001). They arecharacterized by the presence of B-rich and/or Be-bearing minerals such as Al-rich tourmalines, dumortierite,
grandidierite, prismatine, boralsilite, werdingite, chrysoberyl, sapphirine, taaffeite and musgravite (redefined as
ferrotaaffeite-6N3S and magnesiotaaffeite-6N3S; Armbruster 2002) (Grew 1996, 2002). Chrysoberyl is the mostabundant Be-carrier in the abyssal pegmatites whereas
beryl, typical in other classes of granitic pegmatites, ismostly absent. Compared to their magmatic relatives,
abyssal pegmatites including AB-BBe subclass have beenless commonly object of mineralogical and petrologicalstudies (see e.g. Èerný  Ercit 2005; Martin  De Vito
2005).
The pegmatite from Starkoè is a typical example ofabyssal pegmatites of the AB-BBe subclass (cf. Èerný 
Ercit 2005) along with several other localities in the Bohemian Massif (Fig. 1, Table 1; see e.g. Fiala 1954, Losert 1956, Èech 1985, Cempírek 2003, Cempírek 
Novák 2004a, b, Fuchs et al. 2005, Cempírek et al. 2006).
It is located in high-grade metamorphic rocks of the
Gföhl Unit, Kutná Hora Crystalline Complex. Here we
present description of mineral assemblages, chemicalcomposition of minerals, potential substitution mechanisms particularly in tourmaline and dumortierite fromStarkoè and closely related abyssal pegmatite at Bìstvina. The studied localities are compared to other occurrences of the abyssal pegmatites of the AB-BBe subclassin the Gföhl Unit, Moldanubian Zone, and with similar
localities worldwide.
2. General geology and occurrence
Three distinct subunits were distinguished in the Kutná
Hora Crystalline Complex on the basis of their lithology
and metamorphic evolution: Micaschist Zone, Kouøim
Nappe and Gföhl Unit, which is subdivided to the Bìstvina Formation, Malín Formation and Plaòany Formation(Synek  Olivierová 1993). Metamorphic rocks of the
Gföhl Unit underwent three-stage metamorphism and260

Journal of the Czech Geological Society 51/34(2006)

deformation (Synek  Olivierová 1993): (i) HP/HT metamorphic event D1 at P ~ 1624 kbar and T ~ 850950 °C(Vrána et al. 2005, Nahodilová et al. 2005) documented
by abundant relics of granulitic fabrics; (ii) an amphibolite facies shear regime D2 (Synek  Olivierová 1993) at
P ~ 9 kbar, T ~ 750 °C (Nahodilová et al. 2005); (iii)
late reactivation event D3, which affected all previous
fabrics and which is probably associated with the overthrusting of the Malín Formation over both the Micaschist Zone and the Kouøim Nappe (Synek  Olivierová 1993, Kachlík 1999). Partial anatexis is expected athigh PT conditions of kyanite zone but the conditions
have not been specified in detail so far (Nahodilová etal. 2005). Vrána et al. (2005) gave T ~ 670 °C and P ~14 kbar for migmatitic gneiss. Anatexis producing kyanite-bearing leucosome was assumed to follow the event
D2 (Synek  Olivierová 1993).
Metamorphic rocks of Malín and Bìstvina Formations
are locally crosscut by pegmatite bodies. Two distinct
textural types of pegmatites were recognized: (i) Discordant pegmatite veinlets, commonly 13 cm thick, locally containing tourmaline and dumortierite as typical accessory minerals, as well as less abundant apatite, garnet,
arsenopyrite, graphite and kyanite. They occur at localities Kutná Hora-Turkaòk, Starkoè, Bìstvina and Spaèice(Fiala 1954, Losert 1956, Èech 1985, Cempírek 2003).
(ii) Simply zoned pegmatite bodies, up to 0.5 m thick,with very similar mineral assemblages to the type (i), including dumortierite and Al-rich tourmalines. These pegmatites are known only from the Malín Formation, at localities Miskovice and Kuklík near Kutná Hora (Fiala
1954, Losert 1956, Cempírek 2003, Cempírek et al.
2006). These zoned bodies show a slightly higher degreeof fractionation and textural differentiation (Cempírek 
Novák 2004b). Accessory dumortierite and tourmaline
were also found in leucocratic metapelites in this region(Losert 1956, Synek  Olivierová 1993). These rocks,
however, do not exhibit such a high degree of melt segregation and transport like the pegmatites examined,
which exhibit apparent intrusive character.
Starkoè, a famous mineralogical locality of almandine garnet studied by several authors (see e.g., Macháèek

 Slavík 1960), is situated about 8 km ENE of Èáslav,
in the Malín Formation (Fig. 1). Cretaceous sediments
cover this area to a large extent and metamorphic rocks
are exposed in few isolated windows. Discordant pegmatite veinlet, at least 10 m long with constant thickness ofabout 12 cm along the whole outcrop, cuts massive migmatized biotite gneiss. The veinlet is locally folded, generally WNW-trending and steeply dipping about 75° SES,
with sharp contact with the host rock. Muscovite flakes,
up to 0.5 cm in size, are randomly distributed and near
the contact locally deformed. Similar deformation features of muscovite were found along contact of metapegmatites in the Hrubý Jeseník Mts. (Novák et al. 2003).
Bìstvina pegmatite is known only from several museum samples. As dumortierite was found at more than
one locality in close vicinity of Bìstvina (see review of
Cempírek  Novák 2000), the precise position of the pegmatite locality is unknown; it is probably located in theneighbourhood of the road from Bìstvina to Spaèice.
Generally, the veinlet is about 1 cm thick, crosscutting
the host biotite gneiss.
Pegmatite veinlets of the AB-BBe subclass from the
Gföhl Unit are very similar in their shape, size and mineral assemblages (Table 1). They are always hosted inhigh-grade rocks within the Gföhl Unit, particularly along
the easternmost border of the Moldanubian Zone (Fig. 1).
The Starkoè pegmatite represents the best developed andcurrently the best exposed locality of abyssal pegmatites
in the Bohemian Massif.
3. Methods
Chemical composition of minerals was obtained using
electron microprobe Cameca SX 100 at the Dionýz túr
Institute of Geology, Bratislava. Analytical conditions:accelerating voltage 15 kV, beam current 20 nA; beam
diameter 15 µm. Following standards were used:Na  albite, Ca, Si  wollastonite, K  orthoclase,
Mg  MgO, Fe  Fe2O3, Cr  chromite, Mn  rhodonite, Al  Al2O3, Ti  TiO2, Cl  NaCl, F  BaF2. Data
were reduced using the PAP routine (Pouchou  Pichoir1985). The chemical formulae of tourmaline wereT a b l e 1 Mineral assemblages of abyssal pegmatites from Gföhl unit. Data from Cempírek (2003) and Cempírek  Novák (2004).
Pegmatite

Primary mineral assemblage

Prograde metamorphic
mineral assemblage

Retrograde metamorphic
mineral assemblage

StarkoèPlg + Qtz + Ms + Grt +Tur I + Dum I + Cbr

Qtz II + Plg II + Ky + Kfs +Tur II + Dum II + St

pyrophyllite, kaoliniteBìstvina

Qtz I + Plg + Ms +Dum I + Tur

Qtz II + Dum II± sillimanite (?)

fine-grained phyllosilicates

Vémyslice

Kfs + Plg + Qtz I +Bt + Dum

Qtz II + sillimanite (?)

muscovite, fine-grained phyllosilicates

Miskovice

Kfs + Plg + Qtz +Ms I + Tur + Dum

Qtz + Dum II (?)

Ms II

Kutná Hora  Kuklík

Early: Plg + Kfs + Qtz + Tur I

Qtz + Dum II

Ms (± symplesite)

Late: Qtz + Cb + Dum I +Tur II + arsenopyrite

Journal of the Czech Geological Society 51/34(2006)

261

Fig. 1 Dumortierite occurrences in the Gföhl Unit in the Czech Republic and Austria, and position of studied localities Starkoè (ST) and Bìstvina (BS). Map modified after Chlupáè et al. (2002), data from Cempírek  Novák (2000).
Symbols:A  major occurrences in boron-bearing granulites and migmatites (localities in vicinity of Kutná Hora and Jemnice)B  rare occurrences in granulites, migmatites and gneisses (from W to E: Pleovice, Malonty near Kaplice, Vanov, Jihlava, Pohled near Havl.
Brod, Raèice near Hrotovice, Horní Bory, Vojetín near Bystøice n. P.)C  occurrences in abyssal pegmatites (from N to S: Kutná Hora  Kuklík, Miskovice, Starkoè, Bìstvina, Vémyslice, Trstìnice, Gföhl, Klein
Pochlarn)
Explanation of the map:
1  Monotonous (Ostrong) series
2  Varied (Drosendorf) series
3  Gföhl Unit with ultrabasic bodies
4  granulites of the Gföhl Unit
5  Bavarian part of Moldanubicum
6  granitoids
7  crystalline units outside of Moldanubicum
8  unmetamorphosed units outside of Moldanubicum
9  limnic Permian cover
10  outer contour of Mesozoic and younger sediments

262

calculated on the basis of sites T+Z+Y=15, assuming total
Fe as Fe2+, Li = 0 and OH preferentially present in the
V-site.
Cathodoluminescence study was done on instrument
HC2-LM with technology of hot luminescence,equipped with SIMON  NEUSER microscope.
Whole-rock chemical analyses were performed at the
Acmé Chemical Laboratories Ltd, Vancouver, Canada, by
ICP  ES (major oxides, Ba, Ni, Sc, Mo, Cu, Pb, Zn, As,
Cd, Sb, Bi, Ag) and ICP  MS (Co, Cs, Ga, Hf, Nb, Rb,
Sn, Sr, Ta, Th, Tl, U, V, W, Zr, Y and REE).
4. Petrography and bulk geochemistry of host rocks
and pegmatites
Massive biotite gneiss at Starkoè contains locally large
porphyroblasts of garnet enclosed in felsic leucosome.
The mineral assemblage of gneiss is: quartz + plagioclase+ Ti-rich biotite (XMg ~ 0.510.53) + garnet I (Alm71
Prp1612Sps14-4Grs115) ± kyanite, the leucosome consists
68
of a fine-grained assemblage: quartz + plagioclase + Kfeldspar with accessory apatite, dumortierite and tourmaline. Porphyroblasts of homogeneous violet-red garnet II(Alm77Prp16Sps5Grs2) commonly volumetrically predominate over the host leucosome. The mineral assemblages
and textural relations suggest that the rock underwent
several metamorphic and deformation events similar to
the rocks in the Bìstvina granulite (Vrána et al. 2005,
Nahodilová et al. 2005). However, they were not studied in a greater detail at the Starkoè locality. At Bìstvina, the precise location of the pegmatite is unknown;
therefore petrography of the host rock could not be
studied.
Chemical compositions of host massive biotite gneiss(leucosome portions not included) and pegmatite are given in Table 2. At Starkoè, the gneiss and pegmatite ex-

Journal of the Czech Geological Society 51/34(2006)

hibit similar concentrations of SiO2 (7173 wt.%), Al2O3(1315 wt.%), CaO (1.561.77 wt.%) and Na2O (2.39
3.05 wt.%). They differ particularly in higher concentrations of Fe2O3 (5.45 versus 1.571.58), MgO (1.79 versus 0.200.35) and TiO2 (0.74 versus 0.100.05) in hostrock, and higher K2O (2.302.95 versus 1.78) in pegmatite (all in wt.%). The pegmatite is enriched in As, Ba,
Ga and Sr, whereas host rock is apparently enriched in
Cs, HFSE and REE. The chondrite-normalized REE patterns of host rocks and pegmatite are very similar disregarding higher concentrations of REE and a weak enrichment in HREE in metapelite (Fig. 2). Chemicalcompositions of host biotite gneisses at Starkoè andBìstvina including their REE patterns are very similar tofelsic granulite type II, migmatite gneiss and granulitic
gneiss in the Bìstvina granulite body, respectively (Vrána et al. 2005).
5. Petrography and mineralogy of the pegmatites
5.1 Starkoè pegmatite
The mineral assemblages and textural relations indicate
the presence of at least three individual stages in the
Starkoè pegmatite evolution. (i) Primary igneous (magmatic) assemblage  plagioclase I + quartz + muscovite+ tourmaline I + garnet III + dumortierite I ± chrysoberyl is volumetrically dominant. (ii) Prograde metamorphic
stage includes: a) newly-formed fine-grained assemblageof K-feldspar + kyanite + quartz replacing muscovite +plagioclase I, together with small amounts of staurolite;b) recrystallization of dumortierite I and tourmaline I producing new generations of dumortierite II and tourmaline II; c) corrosion of chrysoberyl; (iii) Retrograde metamorphic assemblage involves pyrophyllite and kaolinite,
formed by replacement of muscovite and feldspars in

Fig. 2 Chondrite-normalized REE patterns (Boynton 1984) of Bìstvina andStarkoè gneisses and pegmatite.

Journal of the Czech Geological Society 51/34(2006)

263

T a b l e 2 Whole-rock analyses of the studied rock types.
localityrock typeBìstvina
gneissStarkoègneissStarkoèpegmatite

Starkoèpegmatite

55.36
0.92
21.13
7.64
0.09
2.94
0.70
2.21
5.07
0.08
2.90
0.00
99.04

71.44
0.74
13.31
5.45
0.09
1.79
1.56
2.81
1.78
0.11
0.80
0.04
99.92

72.93
0.10
14.93
1.57
0.02
0.35
1.72
2.39
2.92
0.01
2.80
0.21
99.95

73.28
0.05
15.03
1.59
0.02
0.20
1.77
3.05
2.30
0.03
2.60
0.16
100.08

2.0
760.0
0.5
0.3
22.0
9.5
52.0
30.0
3.9
1.0
14.7
70.0
4.0
249.0
0.7
20.0
8.0
126.0
1.2
12.3
0.8
3.5
140.0
1.0
27.0
133.0
147.0

2.0
383.0
0.5
0.2
11.3
5.3
10.0
15.9
6.3
1.0
11.3
20.0
3.0
92.3
0.5
13.0
4.0
180.0
0.9
10.1
0.3
2.5
69.0
1.0
29.7
78.0
246.0

63.0
1271.0
1.0
0.2
2.0
1.4
9.0
22.6
0.8
0.8
6.2
13.0
2.0
63.2
0.7
6.0
3.0
234.4
0.5
3.6
0.1
2.0
11.0
3.0
11.2
9.0
16.7

65.0
927.0
1.4
0.2
1.5
1.4
14.0
21.3
0.8
1.0
5.0
16.0
4.0
49.3
0.9
3.0
1.0
290.2
0.6
5.5
0.1
3.3
9.0
3.0
12.2
5.0
13.0

La
Ce
Pr
Nd
Sm
Eu
Gd

31.90
64.70
7.60
29.60
5.20
1.20
4.34

37.10
75.90
8.32
32.00
5.80
1.21
5.12

8.80
17.40
1.97
8.00
1.90
0.60
2.07

11.10
22.20
2.63
11.30
2.80
0.69
2.69

Σ LREE[wt.%]
SiO2
TiO2
Al2O3
Fe2O3 *
MnO
MgO
CaO
Na2O
K2O
P 2O 5
LOI
TOT/C
total
[ppm]
As
Ba
Bi
Cd
Co
Cs
Cu
Ga
Hf
Mo
Nb
Ni
Pb
Rb
Sb
Sc
Sn
Sr
Ta
Th
Tl
U
V
W
Y
Zn
Zr
[ppm]

144.54165.45

40.74

53.41

Tb
Dy
Ho
Er
Tm
Yb
Lu

0.69
4.92
1.09
3.12
0.49
3.35
0.51

0.78
5.45
1.15
3.21
0.49
3.39
0.49

0.34
1.94
0.34
0.95
0.14
0.96
0.11

0.38
1.98
0.36
1.05
0.14
1.02
0.13

Σ HREE

14.17

14.96

4.78

5.06

Σ REE

158.71180.41

45.52

58.47

* all Fe as Fe2O3

pegmatite. Similar stages and mineral assemblages were
found in most pegmatite veins from the Gföhl Unit (Table 1; see also Cempírek 2003, Cempírek  Novák
2004a), but chrysoberyl and staurolite are known only
from Starkoè.
5.1.1. Major minerals
Plagioclase I forms subhedral to anhedral grains, with
common polysynthetic twinning lamellae and undulose
extinction in polarized-light microscope. Plagioclase I islocally rimmed by a thin zone of very fine-grained mixture of K-feldspar, kyanite, plagioclase II and quartz II
in contact with muscovite. Plagioclase I and II haveclosely similar chemical composition (Ab78An19Kfs3 
Ab84An15Kfs1). Kaolinization sometimes occurs along
fractures in plagioclase.
Fine-grained anhedral quartz I fills space among
grains of plagioclase I. It also encloses tourmaline I, dumortierite I, and garnet III. Quartz I is locally accumulated in the centre of the veinlet. Extremely fine-grained
quartz II forms veinlets along interfaces of plagioclase I
and quartz I. It contains small grains of kyanite, K-feldspar, muscovite, rare chrysoberyl and sometimes also
dumortierite I, which is corroded and overgrown by needles and fibrous aggregates of dumortierite II. Muscovite forms subhedral flakes, up to 5 mm in size, randomly
distributed within of the pegmatite veinlet. Undulose extinction and deformation are common. The fine-grained
prograde metamorphic assemblage (ii) commonly rims
large flakes of muscovite. Muscovite is locally replacedby pyrophyllite, commonly also in a close vicinity of the
prograde assemblage.
5.1.2. Common accessory minerals
Tourmaline
Tourmaline occurs in two distinct types. Tourmaline I
forms pleochroic (E = colourless, O = light brown-green)prismatic crystals, up to 2 mm in size, commonly
broken and/or corroded. It is enclosed in quartz I andplagioclase I. Pleochroic tourmaline II (E = colourless,
O = dark green) occurs as narrow rims along fractures
or as microscopic spots within tourmaline I. It is typically associated with quartz II.
Tourmaline I and II have quite a wide compositional
range (Table 3, Fig. 3). The T-site exhibits highly variable contents of Si (5.52 to 5.99 apfu). The T-site tends
to be fully occupied by Si in tourmaline II, whereas intourmaline I the T-site contains up to 0.48 apfu TAl. The
Z-site is assumed to be fully occupied by Al, although aminor disorder of Mg between the Y- and Z-sites can be
expected. The Y-site is highly variable in Al, Fe and Mg(Fig. 3a). Composition of the tourmaline I shows vari-264

Journal of the Czech Geological Society 51/34(2006)

T a b l e 3 Chemical composition of tourmaline and dumortierite from Starkoè and Bìstvina.
StarkoèBìstvina

Tur I

Tur I

Tur I Tur II

Dum

Dum

Tur I Tur II

Dum

Dum
30.47

SiO2

35.58

34.56

33.20

35.24

31.14

31.29

35.97

35.86

31.79

TiO2

0.01

0.00

0.01

0.00

0.02

0.05

0.01

0.02

0.29

0.02

Al2O3

37.16

39.42

41.55

34.90

60.71

60.09

37.97

35.40

60.32

59.47

B 2O 3*

10.32

10.45

10.45

10.22

6.01

6.04

10.58

10.46

6.14

5.88

Cr2O3

0.00

0.02

0.00

0.00

0.00

0.00

0.06

0.04

0.00

0.00

MgO

0.67

1.40

1.12

2.60

0.86

0.68

1.79

3.82

0.99

0.82

CaO

0.16

0.42

0.61

0.40

0.00

0.02

0.19

0.29

0.02

0.02

MnO

0.40

0.32

0.39

0.01

0.01

0.02

0.20

0.04

0.02

0.00

FeO

9.97

8.15

7.23

9.45

0.28

0.34

9.16

8.26

0.25

0.29

Na2O

1.50

1.64

1.66

1.63





1.62

1.83

0.03

0.01

K2O

0.04

0.04

0.04

0.05





0.04

0.05

0.01

0.02

H2O*

2.71

2.77

2.76

2.88





2.94

3.00





F

0.05

0.04

0.00

0.07





0.00

0.21

0.07

0.05

Cl

0.02

0.01

0.00

0.01





0.00

0.00

0.01

0.00

O=F

-0.02

-0.02

0.00

-0.03





0.00

-0.09

-0.03

-0.02

O=Cl

0.00

0.00

0.00

0.00





0.00

0.00

0.00

0.00

total

98.57

99.22

99.02

97.43

99.03

98.53

100.53

99.19

99.91

97.03

T

Si

5.993

5.747

5.520

5.996

3.000

3.000

5.911

5.959

3.000

3.000

T

Al

0.007

0.253

0.480

0.004





0.089

0.041





B

3.000

3.000

3.000

3.000

1.000

1.000





1.000

1.000

Al

6.000

6.000

6.000

6.000





6.000

6.000





Al

1.369

1.472

1.661

0.994

6.893

6.790

1.265

0.892

6.709

6.901

Y

Ti

0.001

0.000

0.001

0.000

0.001

0.004

0.001

0.002

0.021

0.001

Y

Cr

0.000

0.003

0.000

0.000

0.000

0.000

0.008

0.005

0.000

0.000

Y

Fe

1.404

1.133

1.005

1.345

0.023

0.027

1.259

1.148

0.020

0.024

Y

Mg

0.168

0.347

0.278

0.659

0.124

0.097

0.439

0.946

0.139

0.120

Y

Mn

0.057

0.045

0.055

0.001

0.001

0.002

0.028

0.006

0.002

0.000

X

Na

0.490

0.529

0.535

0.538





0.516

0.590

0.005

0.002

X

Ca

0.029

0.075

0.109

0.073





0.033

0.052

0.002

0.002

X

K

0.009

0.008

0.008

0.011





0.008

0.011

0.001

0.003

X

vac.

0.472

0.388

0.348

0.378





0.443

0.347





V

OH

3.000

3.000

3.000

3.000





3.000

3.000





W

OH

0.046

0.068

0.056

0.274





0.222

0.326





W

F

0.027

0.021

0.000

0.038





0.000

0.110

0.021

0.016

W

Cl

0.006

0.003

0.000

0.003





0.000

0.000

0.002

0.000

W

O

0.921

0.908

0.944

0.685 17.990 17.820

0.778

0.564 17.759 17.995

ZY* B2O3 and H2O content calculated on the basis of ideal stoichiometry.

able YAl (0.47 to 1.66 apfu) and Fe (0.74 to 1.66 apfu)
and only low amounts of Mg (0.06 apfu). On the other
hand, metamorphic tourmaline II has uniform Fe and Al
contents (Fe ~ 1.161.25 apfu, Al ~ 0.890.74 apfu; see
Fig. 3a) and highly variable content of Mg (0.16 to 0.99
apfu). The contents of Mn (≤ 0.08 apfu) and Ti (≤ 0.01
apfu) are very low in both tourmaline types. The X-site
is characterized by high vacancy (0.48 to 0.31 pfu) inboth tourmaline I and II. This vacancy is slightly higher
in tourmaline I; however, Na (0.59 to 0.49 apfu) prevails
in all cases (Fig. 3b). Only slightly elevated Ca contents(≤ 0.11 apfu) were recorded. Both tourmaline I and II

show low F content (≤ 0.12 apfu) and rather low calculated OH (3.49 to 2.79 apfu; Fig 3c). Although the partitioning of OH between V- and W-sites is not precisely
known, it is clear that tourmaline I shows a significant
fraction of oxy-tourmaline end-member(s), whereas
tourmaline II contains elevated OH in X-site.
Dumortierite
Dumortierite I forms strongly pleochroic (X = bluish,
colourless, Y, Z = pale blue to deep azure blue) subhedral prismatic crystals often twinned along 110, or ag-

Journal of the Czech Geological Society 51/34(2006)

265

A

B

C

Fig. 3 Starkoè and Bìstvina tourmaline composition. A  Y site,
B  X site, C  V+W sites. Analyses with prevailing oxy-tourmaline
end-members exhibit OH < 87.5 in figure 3C.

occur in fine-grained biotite gneiss matrix locally close
to the contact with pegmatite veinlet. Large anhedralgrains of violet-red garnet II, up to 10 cm in size, occur
in fine-grained leucosome of migmatite. It is quite homogeneous; a bulk chemical analysis yielded composition corresponding to Alm77Prp16Sps5Grs2, the EMP study
confirmed its homogeneity and found slightly increased
Mn at rims. The FT-IR spectroscopy has proven that thegarnet II does not contain any water, even at ppm level.
Garnet II from Starkoè was the first recorded occurrenceof water-free almandine garnet at all (Cempírek et al.
2003). Rare grains of subhedral orange-red garnet III(Alm8062Sps3010Prp83Grs32), commonly less than 1 mm
size, were found in pegmatite. Its composition varies in
the individual grains and it is distinctly different from theformer two types, being enriched in spessartine and depleted in pyrope and grossular components. Minute inclusions of monazite-(Ce), xenotime-(Y) and fluorapatitewere found in garnet III.
5.1.3. Other accessory and secondary minerals
Chrysoberyl was found in a single grain about 0.1 x 0.05
mm in size, as strongly corroded crystal among grains ofplagioclase II, K-feldspar and tourmaline I (Fig. 4). Although a patchy zoning of the grain is visible in the BSE
image, no chemical differences between the individualzones were detected. WDA analysis yielded only Al2O3
and very low amounts of SiO2. The calculated sums ofoxides are in good agreement with the theoretical formula
BeAl2O4. The other two possible Al-rich minerals, gibbsite and diaspore, yielded much lower or higher calculated sum of oxides. This strongly supports the identityof chrysoberyl, which fits best to the WDA analyses.
Kyanite occurs in fine-grained aggregates associatedwith quartz II, K-feldspar (Kfs9588Ab512), plagioclase II
and rare staurolite (Figs 5 and 6). Minerals of this prograde metamorphic assemblage typically form irregulargregates of needle-like or fibrous crystals, up to 3 mm
long, locally associated with tourmaline I. The crystals
commonly exhibit features of shearing and recrystallization. Dumortierite II forms colourless, needle-like to fibrous aggregates enclosed in quartz II, overgrowing corroded grains of dumortierite I or rarely tourmaline I.
Dumortierite has variable but low contents of Mg (0.05
to 0.12 apfu), a uniform very low content of Fe (0.03
apfu), and traces of Ti. The Al/Si ratio is rather low (Al~ 6.8 at Si = 3). Dumortierite (Table 3) is expected tocontain stoichiometric amount of B.
GarnetThree morphologically and compositionally distinct typesof garnet were recognized in gneiss and pegmatite atStarkoè. Small subhedral red to red-brown grains of garnet I (Alm7168Prp1612Sps14-4Grs115), up to 1 mm in size,

Fig. 4 Corroded grain of chrysoberyl, at the contact with tourmaline I,
K-feldspar and plagioclase II. Starkoè pegmatite. Scale bar is 20 µm.

266Journal of the Czech Geological Society 51/34(2006)cated by the scarcity of the quartz II, tourmaline II anddumortierite II and by the absence of kyanite and staurolite. However, only several samples from this pegmatite are known which do not enable such a detailed characterization of the mineral assemblages comparing to
Starkoè.
5.2.1. Major minerals

Fig. 5 CL-photograph of fine-grained aggregate of kyanite (light blue)+ K-feldspar (blue) + quartz II (dark), within altered contact of muscovite crystal (black) with plagioclase II (yellow). Few grains of apatite (green) are present. Picture width is about 0.6 mm.

Anhedral grains of quartz I encloses crystals of plagioclase I, muscovite, tourmaline and dumortierite. Quartz
is the prevailing mineral of the veinlet. Fine-grained
quartz II is very rare; it forms thin veinlets, locally enclosing dumortierite I and II.
Plagioclase I (Ab82An15Kfs2) forms subhedral to anhedral elongated grains and crystals, with common
polysynthetic twinning lamellae. Its crystals are often
oriented perpendicularly to the pegmatite border. Plagioclase is commonly slightly replaced by fine-grained phyllosilicates, rarely by dumortierite II.
Muscovite forms euhedral crystals, up to 10 mm insize, commonly oriented perpendicularly to the pegmatite border. Undulose extinction is common. Muscovite
commonly encloses dumortierite I, locally also dumortierite II at the rims of muscovite crystals.
5.2.2. Common accessory minerals

Fig. 6 Fine-grained aggregate of kyanite + quartz II + plagioclase II+ K-feldspar, within altered rim of muscovite crystal, at the contact withquartz I. Spotty light grain at the bottom left is staurolite with inclusions of quartz II. Darker rim of muscovite is formed by pyrophyllite.
Scale bar is 50 µm.

grains less than 50 µm in diameter, only staurolite wasfound as intergrowths with quartz in few grains up to
100 µm in size. Staurolite is rather poor in Mg (0.320.38
apfu) and rich in Fe (2.983.15 apfu) with variable contents of Si and Al (7.67.9 apfu Si, 18.518.0 apfu Al),
concentrations of other elements are low. Rare accessory minerals include fluorapatite, monazite-(Ce) and xenotime-(Y) as rare inclusions in garnet III, and löllingite. They were not studied in detail.
5.2 Bìstvina pegmatite
Pegmatite from Bìstvina exhibits similar mineralogy andtextural relations as Starkoè pegmatite (Table 1). The
metamorphic overprint is less developed, which is indi-Dumortierite from pegmatite at Bìstvina is also represented by two generations. Primary dumortierite I strongly prevails over rare dumortierite II. Long-prismatic subhedral crystals of pleochroic dumortierite I (X =yellowish, colourless, Y, Z = pale bluish to deep azureblue) are mostly enclosed in muscovite, sometimes alsoin quartz. When enclosed in quartz, it commonly forms
crystals twinned along 110. Fibrous pleochroic dumortierite II (pleochroic colours same as dumortierite I) is
quite rare, it was found overgrowing the primary dumortierite I or in thin veinlets of fine-grained quartz II. The
chemical composition of Bìstvina dumortierite is very
simple, besides rather stoichiometric Al and Si only low
content of Mg (up to 0.15 apfu) and very low Fe and Ti(up to 0.05 apfu) were found (Table 3).
5.2.3. Other accessory and secondary minerals
Tourmaline from pegmatite at Bìstvina was found in asingle anhedral, strongly brecciaed grain. Chemical data
indicate two generations of tourmaline, compositionallyvery similar to the Starkoè tourmaline (see Fig. 3). The
amount of the prograde metamorphic tourmaline II inBìstvina seems to be very low and limited to thin fractures or zones within the primary tourmaline I.
Colourless fibrous sillimanite (?) was rarely observed
together with the fibrous dumortierite II. Its identity was
not proved by any analysis.

Journal of the Czech Geological Society 51/34(2006)

267

Composition of tourmaline from abyssal pegmatites at
Starkoè and Bìstvina is controlled by their two-stage origin. Fractionation of Fe, Mn, Mg and Al in primary tourmaline I is of special interest. In tourmaline I fromStarkoè the (Fe+Mn)/Mg ratio decreases with increasing
Altot, whereas in quite homogeneous tourmaline I fromBìstvina this ratio is constant along with this increase(Fig. 7). Because the analytical points in Fig. 7 represent
core-to-rim zonality in several crystals, the data can be
regarded as a fractional crystallization of tourmaline I.
Such a reversed fractionation as expressed by (Fe+Mn)/
Mg ratio in tourmaline I from Starkoè is unusual if compared to other tourmaline data from abyssal pegmatites
in the Gföhl Unit (Fig 7; see also Cempírek 2003) andfrom granitic pegmatites worldwide. The compositional
evolution of tourmaline from schorl-dravite-foitite to elbaite-rossmanite-olenite and an increase in (Fe+Mn)/Mg
ratio are general geochemical trends found in most typesof granitic pegmatites (see e.g. Selway et al. 1999, Novák
2000, Cempírek  Novák 2004b). The reason for the reversed fractionation trend in Starkoè tourmaline is unknown.
The prograde metamorphic event introduced additional Fe and Mg from the host rock into the system and remobilization of B allowed crystallization of tourmaline II.

The breakpoint in evolution is visible in (Fe+Mn)/Mg
ratio (Fig. 7), where sum of Fe+Mg+Mn increases via substitution for Al in both Y- and Z-sites. At both localities,
the (Fe+Mn)/Mg ratio in secondary tourmaline II is very
close to that in the host metamorphic rock (Fig. 7).
The primary tourmaline I is typical by its high Al-content and incorporation of Al into the T-site, whereas thesecondary tourmaline has rather stoichiometric Si content in T-site. The elevated content of Al in T-site is atypical feature of tourmaline from abyssal pegmatites(Cempírek 2003, Cempírek et al. 2006). Tourmaline I
from Starkoè is Al-rich (up to 1.66 apfu in Y-site, up to
0.48 apfu in T-site), in Bìstvina the content of TAl is rather low (up to 0.2 apfu). Very high contents of Al (up to
2.2 apfu in Y-site, up to 0.52 apfu in T-site) were foundin tourmaline at other localities of the region (Miskovice, Kuklík; Cempírek 2003, Cempírek et al. 2006),
where Al2SiO5 minerals are absent. The deficiency of Si
in the T-site might be also explained by the presence ofT
B instead TAl. Although B was not analyzed, the authors
do not expect significant amount of TB due to moderate
activity of B in the system. It is well demonstrated by
the presence of kyanite besides tourmaline and dumortierite. Primary tourmaline I from Starkoè and Bìstvina
with low variability in the X-site exhibits crystallization
trend expressed by substitution vector (Y,ZAl TAl)(Y,ZR2+
TSi4+)-1 or by combination of vectors (Al3+OH)(SiO2)-1and (AlO2)(R2+OH)-1 in 1:1 ratio. Metamorphic tourmaline II is rather homogeneous and does not exhibit clear
substitution trends (Fig. 8).

Fig. 7 Fractionation trends of (Fe+Mn)/Mg ratio versus total Al in tourmaline from abyssal pegmatites in the Gföhl unit. Horizontal line at(Fe+Mn)/Mg = 1.6 shows the value for host rock (gneiss) at Starkoè.

Fig. 8 Compositional trends of tourmaline from Starkoè and Bìstvina.

6. Discussion
6.1. Compositional evolution and substitution
mechanisms in tourmaline and dumortierite

268

Dumortierite was found in two textural types. Primary dumortierite I forms prismatic crystals of blue to violet
colour, up to 5 mm long, whereas dumortierite II forms
fibrous aggregates of very light colour or colourless.
Composition of primary dumortierite I is rather simple,
with a very low contents of minor elements (Fe, Mg, Ti). Thevery low colour intensity indicates that content of minor
elements in fibrous dumortierite II is extremely low. Dueto a very low amount of other analyzed elements than Al
and Si, it was not possible to chemically distinguishbetween the two textural generations of dumortierite,
although textural and optical differences are apparent.
At other localities (Kuklík and Miskovice near Kutná
Hora; Fiala 1954, Losert 1956, Cempírek 2003), a similar dumortierite with light colour in shades of green
was found. Very low Fe, Mg, Ti contents and smaller unit
cell parameters are their typical features (unpublisheddata of JC).
Besides variation in minor elements, dumortierite hasvariable contents of the dominant elements and variable
Al/Si ratio (Table 3). This ratio is highly sensitive to analytical conditions but the variation in composition isseen even among analytical spots within the same analytical set. Water in dumortierite was not determined but
only calculated on the basis of electrochemical neutrality. Variation in Al/Si ratio can be explained by the substitution vectors (OH) 3[AlO 3] -1 and Al(OH)[SiO] -1,
which both incorporate OH into the structure of dumortierite. The former substitution seems to be most likely
dominant.
6.2. Comparison with other AB-BBe subclasspegmatites in the Moldanubian Zone
The examined pegmatite veinlets from Starkoè and Bìstvina exhibit typical paragenetic and textural features ofabyssal pegmatites of the AB-BBe subclass (see e.g.
Èerný  Ercit 2005, Grew et al. 2000), such as the presence of Al-rich minerals, close relations to HP/HT metamorphic host rock, small thickness, elevated content oflight elements (B, Be), and polyphase evolution. The discordant pegmatite veinlets from Vémyslice and Trstìnice
near Moravský Krumlov are the only mineralogicallysimilar localities known in the Bohemian Massif. Theseabyssal pegmatites exhibit thin veinlets, polyphase evolution, sharp contact with host rock and abundant dumortierite. In the case of Vémyslice locality the principal differences from the studied pegmatites include high bulk
K2O content, abundant K-feldspar but only secondary
muscovite, presence of biotite and metamorphic sillimanite and elevated As in dumortierite (Cempírek  Novák
2004). The presence of sillimanite and biotite in Vémyslice instead of Al-rich tourmaline may suggest lower
activity of B relative to Starkoè. Associated younger
abyssal pegmatite veinlets containing oscillatory zoned
tourmaline with moderate amounts of Al, graphic tourmaline + quartz intergrowths and andalusite are likely
related to some LP event. Information about other abys-

Journal of the Czech Geological Society 51/34(2006)

sal pegmatites with dumortierite from the Austrian partof the Moldanubian Zone (Miesling, Gföhl, Klein
Pochlarn) is scarce; hence detailed comparison is notpossible.
Simply zoned abyssal pegmatites from Kuklík andMiskovice exhibit a different internal structure, but theirmineralogy is similar to the pegmatite veinlets at Bìstvina and Starkoè. The main differences exist in internal
structure showing the zoned development, a larger thickness of pegmatite bodies, transitional contacts, presenceof enclaves of host rocks, and less apparent metamorphic
overprint. A significant interaction with xenoliths suggests higher contents of volatiles, including B, in thezoned abyssal pegmatites. It is also supported by a higher degree of fractionation, which is indicated by tourmaline composition (Fig. 7), and also by dumortierite composition, including late green dumortierite extremely poorin minor cations (Fe, Mg, Ti).
Disregarding the largely textural differences observedin the discordant pegmatite veinlets (Starkoè, Bìstvina,
Vémyslice) and the simply zoned abyssal pegmatites(Kuklík, Miskovice), they exhibit many similar features,
namely almost identical mineral assemblages including
accessory minerals. It suggests that they originated atsimilar PTX-conditions and that they are closely related
to similar geological events.
6.3. Comparison with other AB-BBe subclasspegmatites from the world localities
Gay and Galliski (1979) reported from Virorco, San
Luis, Argentina, mineral assemblages most similar to
those described from abyssal pegmatites at Starkoè andBìstvina. At Virorco, two distinct types of pegmatites
crosscut gabbros and norites within terrane formed by
granulites and quartzites. The first one forms fine-grained
veinlets, about 23 cm thick, with quartz, blue and green
dumortierite, two types of tourmaline (black to blue andgreen to colourless), kyanite, plagioclase An10, muscovite,
apatite, sillimanite and staurolite. The second pegmatite
type forms coarser grained (2.50.5 cm) veins, up to 10
cm thick, consisting of quartz, plagioclase (Ab9288An8
), pinkish muscovite, black tourmaline, garnet, stauro12
lite, chrysoberyl and blue dumortierite. Dumortierite occurs only in central parts of veins rich in quartz, whereas
staurolite was found only in nodules with garnet or kyanite. Prismatic dumortierite I is commonly overgrown by
fibrous dumortierite II and forms aggregates with quartz,
muscovite and tourmaline. It is also locally replaced bykyanite and tourmaline. Two generations of dumortierite from Virorco pegmatites exhibit features very similar
to those from Starkoè and Bìstvina pegmatites. The presence of staurolite, kyanite, two generations of dumortierite and tourmaline replacement by other minerals suggests a polyphase evolution of the Virorco pegmatites.
Almgjotheii pegmatite, Norway, represents anotherabyssal pegmatite similar to Starkoè (Huijsmans et al.
1982, Grew et al. 1998a, b). It is located in garnetifer-

Journal of the Czech Geological Society 51/34(2006)

ous migmatite and originated during their anatexis at
550700°C and 35 kbar. Besides primary (magmatic)
assemblage involving the following accessory minerals(dumortierite, andalusite, sillimanite, grandidierite, garnet), two prograde stages and one retrograde metamorphic stage were recognized. The prograde events produced werdingite, boralsilite, dumortierite II, sillimanite,
grandidierite II, tourmaline, corundum, hercynite andandalusite II, all by the reaction of primary minerals withmetamorphic fluids. Retrograde metamorphic phase isrepresented by sericite, chlorite and margarite (Grewet al. 1998b).
Thin veinlets of dumortierite-bearing pegmatites similar to Starkoè also are known from the Saxony Granulite Complex at the locality Hartmansdorf quarry (Vollstädt  Weiss 1991, Anderson et al. 1998). However,mineralogy of these pegmatites was not studied in a greater detail.
7. Conclusions
All known pegmatites of AB-BBe subclass in the Bohemian Massif occur in the Gföhl Unit (Kutná Hora Crystalline Complex, Moravian Moldanubicum, Moldanubicum of Waldviertel in Lower Austria), apparently along
the easternmost border of the Moldanubicum (Fig. 1).
Where studied in detail (Bìstvina Granulite, Kutná Hora
Crystalline Complex), HP metamorphic conditions ofabout 1824 kbars in the host rocks and rapid exhumation were revealed (Vrána et al. 2005). These host rocks
also exhibit low degree of MP overprint and such metamorphic evolution is a typical feature of host rocks ofabyssal pegmatites in the high-grade terrains of Antarctica and Madagascar (Grew 1998). The presence of kyanite in some pegmatite bodies and in migmatitic leucosome suggests HP conditions of melting (cf. Nahodilová
et al. 2005), but not specified in detail. Moreover, kyanite in Starkoè is a product of prograde metamorphic overprint; hence this overprint preceded relatively HP conditions as well.
Geological position of abyssal pegmatites of the ABBBe subclass in the Moldanubian Zone, such as apparent HP conditions of their origin and their absence in theother parts of the Moldanubian Zone indicate quite specific conditions necessary for generation of this type of
pegmatites. Unfortunately, the host rocks of abyssal pegmatites were studied in detail only in a part of the Kutná
Hora Crystalline Complex (Vrána et al. 2005). Although
the individual known localities of AB-BBe subtype pegmatites in the Gföhl Unit are distant from each other, we
expect them to originate during rather similar metamorphic processes which significantly affected their hostrocks. Future research is necessary to reveal relations
between abyssal pegmatites examined and geologicalevolution of their host rock complexes, including metamorphic overprints. Because similar conditions were
found in other metamorphic terrains containing abyssal

269

pegmatite of the AB-BBe subclass (see e.g., Grew 1996,
1998), dumortierite-bearing abyssal pegmatites may become a good indicator of HP-metamorphic conditions
with a weak MP overprint and of a rapid exhumation in
high-grade metamorphic terrains.
Acknowledgements. The authors thank to the reviewers
dr. Stanislav Vrána and prof. Wali S. Faryad for constructive comments that significantly improved the manuscript. This work was supported by the research projects
MK00009486201 to JC and MSM 21622412 to MN.
Submitted November 13, 2006
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Mineralogie abysálních pegmatitù s dumortieritem ze Starkoèe a Bìstviny, Kutnohorské krystalinikum
Abysální pegmatity ze Starkoèe a Bìstviny jsou typickými zástupci podtøídy AB-BBe abysálních pegmatitù v Èeském masivu. Znaky typické pro jejichpùvod a vývoj jsou nejlépe zachovány v pegmatitu Starkoè, kde byly na základì paragenetických vztahù rozlieny 3 asociace: (i) Primární magmatická
asociace: plagioklas I + køemen I + muskovit + granát III + turmalín I + dumortierit I + chrysoberyl; (ii) Prográdní metamorfní asociace: køemen II +plagioklas II + kyanit + K-ivec + staurolit + turmalín II + dumortierit II; (iii) Retrográdní metamorfní asociace: pyrofylit a kaolinit. Plagioklas, køemen
a muskovit jsou hlavními minerály pegmatitové ilky; mezi èasté akcesorie patøí turmalín, dumortierit, granát, K-ivec a kyanit, pouze velmi vzácnì bylnalezen submikroskopický chrysoberyl, staurolit a nìkolik dalích akcesorických minerálù. Sloení turmalínu je silnì ovlivnìno dvoufázovým vývojem
pegmatitu. Sloení primárního turmalínu I na lokalitì Starkoè vykazuje trend blízký substituci (Y,ZAl TAl)(Y,ZR2+ TSi4+)-1. Pozdìjí prográdní metamorfní
event dodal do systému Fe a Mg z okolní horniny a remobilizace bóru zapøíèinila krystalizaci homogenního turmalínu, který je obohacen o Mg. Starkoè,Bìstvina a vechny dalí známé abysální pegmatity podtøídy AB-BBe v Èeském masivu se objevují v Gföhlské jednotce, podél východní hranice
Moldanubika. Okolní horniny abysálních pegmatitù vykazují znaky HP metamorfózy se slabými projevy MP metamorfózy. Tento metamorfní vývoj jetypickým znakem i pro horniny s podobnými abysálními pegmatity v Antarktidì, Norsku a na Madagaskaru.